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A filter element is formed from a strip of filter paper having a regularly
spaced series of transverse fold lines, two lines of adhesive being
respectively applied to one edge on one face of the strip and to the
opposite edge on the opposite face of the strip, the strip then being
formed into pleats by folding about the transverse fold lines, the two
halves of each pleat being sealed to each other at one end of the assembly
but at the other end being sealed to the adjacent halves of adjacent
pleats to each side thereof, so as to form a series of pockets which are
open alternately at the top and the bottom of the assembly, and the ends
of the assembly of pleats being sealed to each other to form it into a
hollow tubular element which may then be fitted into a housing with a
center tube and end plate assembly, the element being sealed at one end to
the housing and at the other end to the center tube.

1. A filter unit comprising a filter element formed from a strip of sheet filter material having two lines of adhesive respectively applied to opposite faces of the strip adjacent
opposite longitudinal edges thereof, the strip being folded about a series of regularly spaced fold lines extending transversely of the strip to form an assembly of accordion pleats, the two halves of each pleat being sealed to each other, at one end of
the pleat, and, at the other end thereof, being sealed respectively to the adjacent halves of adjacent pleats to each side thereof, and the ends of said strip being secured and sealed to each other to form the assembly into a hollow tubular filter
element; a combined center tube and end plate assembly having an annular end plate with a central flanged opening adapted to be fitted over a spigot in a filter head, and a center tube which extends coaxially from one face of said end plate; and a
tubular casing having at one end thereof a centrally apertured base with an annular internal shoulder thereon adjacent the wall of the casing, said filter element being fitted over said center tube and sealed at its inner periphery at one end thereof to
the angle between the end plate and center tube, the free ends of the pleats adjacent said one end being at the outer periphery of the element, and the assembled filter element, end plate and center tube being fitted within said casing with the other end
of said element seated on said internal shoulder, the outer periphery of the element at said other end being sealed to the annular shoulder, and the outer periphery of said end plate being sealed to the casing at the other end thereof.

2. A filter unit according to claim 1, in which said end plate has openings therein overlying the ends of said pleats.

3. A filter unit according to claim 2, in which said casing base is formed with openings therein.

4. A filter unit according to claim 1, in which said center tube fits within and is sealed to said base, said end plate and base having openings therein adjacent the ends of said pleats of the element, said element being spaced at its inner
periphery from said center tube and said end plate being formed with impressed channels providing communication between the openings in said end plate and the space between the center tube and the element.

Description

This invention relates to filter elements for liquid filters and in particular to filter elements, and filter units including such filter elements, for use in the filtration of liquid fuels for internal combustion engines.

A filter element according to the present invention is formed from a strip of sheet filter material having two lines of adhesive respectively applied to opposite faces of the strip adjacent opposite longitudinal edges thereof, the strip being
folded about a series of regularly spaced transverse fold lines to form an assembly of accordian pleats, the two halves of each pleat being sealed to each other, at one end of the assembly, and, at the other end of the assembly, being sealed respectively
to the adjacent halves of adjacent pleats to each side thereof.

The ends of the assembly of pleats thus formed may be secured and sealed to each other to form the assembly into a hollow tubular filter element.

In order to form a filter unit which may be readily fitted into a fuel filter of known kind, in which a hollow tubular element is clamped between a filter head and a bowl for the collection of water droplets which have separated out from the fuel
during filtration, the tubular fitted element may be fitted over the central hollow spigot of a combined center tube and end plate assembly which is conveniently formed of plastics, comprising an annular end plate with a central flanged opening adapted
to be fitted over a spigot in a filter head and a center tube which extends coaxially from one face of the end plate and is integral therewith. The filter element fits over the center tube and at its inner periphery is sealed by adhesive to the angle
between the end plate and center tube, the free ends of the pleats at that end being at the outer periphery of the element.

The center tube and end plate with the filter element fitted thereon is then inserted in a tubular casing or shell having a base with an annular internal shoulder thereon on which the other end of the filter element is seated, the outer periphery
of the element at that end being sealed to the annular shoulder by adhesive.

The casing is conveniently made of sheet metal and the base thereof has a central aperture and is formed with a neck which locates the free end of the center tube. The base is spaced by the annular shoulder from the other end of the filter
element and is formed with a plurality of openings therein.

The end plate is sealed at its outer periphery to the wall of the casing.

It will be understood that with the construction of the filter element described the positions of the seals between the ends of the element and the casing and center tube and end plate will be reversed if the position of the filter element is
reversed end for end relative to the end plate and center tube.

In use the filter unit formed as described above is clamped between a seat on a filter head and an annular seat on a cup or like container which is secured to the filter head by a bolt passing coaxially through the cup and filter head. The
filter head has a central spigot with an annular gasket located in an external groove therein, the end plate of the filter unit fitting over and being sealed to the central spigot of the filter head.

The scope of the invention is defined by the
appended claims; and the invention and the method by which it is to be performed are hereinafter particularly described with reference to the accompanying drawings in which:

FIG. 1 is a plan of a strip of sheet filter material in the course of its formation into a filter element in accordance with the invention;

FIG. 2 is a view on the line II--II of FIG. 1;

FIG. 3 is a section on the line III--III of FIG. 1;

FIG. 4 is a perspective view showing a portion of a filter element in accordance with the invention;

FIG. 5 is a composite vertical section through a fuel filter assembly incorporating a filter element according to the invention, the left hand side of the drawing showing liquid flow through the assembly from a passage in the filter head to the
top of the filter unit, through the element, and then to a central passage in the filter unit, and the right hand side showing liquid flow from the central passage in the filter unit, through the element, and then from the upper end of the element to a
passage in the filter head;

FIG. 6 is a vertical section of a modified form of the filter unit shown in FIG. 5; and

FIG. 7 is a plan of FIG. 6.

Like parts in the drawings bear similar reference numerals.

In order to form a filter element according to the invention a strip 1 of filter paper, which may be crepe paper impregnated with synthetic resin, or containing synthetic resin incorporated in the paper during its manufacture, or may be synthetic
resin impregnated filter paper, is used. The paper strip 1 has a line of adhesive 2 applied to one face thereof along one longitudinal edge of the strip 1, and a further line of adhesive 3 applied to the opposite face of the strip adjacent the opposite
longitudinal edge thereof. The strip is then folded about regularly spaced transverse fold lines 4 to form an assembly of accordian pleats 5, the two halves of each pleat being sealed to each other, at one end of the assembly, and, at the other end of
the assembly being sealed respectively to the adjacent halves of adjacent pleats to each side thereof, as shown in FIGS. 1, 2 and 3.

The paper may have spacer dimples or other spacer formations impressed therein, as is known in the art, to space adjacent pleats, and the two halves of each pleat, from each other, but such formations are omitted from the drawing for the sake of
clarity.

The ends of the strip thus formed into an assembly of pleats may be secured and sealed to each other to form the assembly into a hollow tubular filter element 6, as shown in FIG. 4.

FIG. 5 shows the manner in which the filter element 6 is formed into a filter unit 7 which is fitted into a fuel filter of known kind, the filter unit 7 being clamped between a filter head 8 and a bowl 9 for the collection of water droplets which
have separated out from the fuel during filtration, the tubular filter element 6 being fitted over a central tube 10 which is integral with a coaxial end plate 11 and forms a combined center tube and end plate assembly which is conveniently made of
plastics, the end plate 11 being of annular form and having a central opening around which extends a flange 12 which is adapted to fit over a central hollow spigot 14 in the filter head 8 and is sealed thereto by engagement with a seal ring 15 located in
an annular recess in the outer periphery of the spigot 14.

The filter element 6 fits over the center tube 10 and at its inner periphery is sealed by adhesive 16 to the angle between the end plate 11 and center tube 10, the free ends of the pleats of the element 6 at that end being at the outer periphery
of the element.

The center tube 10 and end plate 11 with the filter element 6 fitted thereon is arranged within a tubular casing or shell 17 having a base 18 with an annular internal shoulder 19 thereon on which the other end of the filter element 6 is seated,
the outer periphery of the element 6 at that end being sealed to the annular shoulder 19 by adhesive 20.

The casing 17 is conveniently made of sheet metal and the base 18 thereof has a central aperture and is formed with a coaxial neck 21 which locates the free end of the center tube 10. The base 18 is spaced by the annular shoulder 19 from the
other end of the filter element 6 and is formed with a plurality of lanced openings 22 therein.

The end plate 11, at its outer periphery, is sealed, as by adhesive, to the wall of the casing 17.

It will be understood that with the construction of the filter unit 7 described the positions of the seals 16 and 20 between the ends of the element 6 and the casing 17 and center tube 10 will be reversed (as shown in FIG. 6) if the position of
the filter element 6 is reversed end for end relative to the end plate 11 and center tube 10.

In use, the filter unit 7 formed as described above is clamped between an annular seat 24 on the filter head 8 and an annular seat 25 at the open end of the bowl 9 which is secured to the filter head 8 by a bolt 26 passing coaxially through the
bowl 9 and filter head 8. The filter unit 7 is sealed to the spigot 14 by the seal ring 15, and gaskets 27 and 28 are interposed respectively between the upper end of the filter unit 7 and the seat 25 and the lower end of the filter unit and the seat
25.

The end plate 11 has therein openings 21 which overlie the spaces between the ends of the pleats of the filter element 6 and are in communication with an inlet passage 32 in the filter head, the space within the center tube 10 being in
communication with an outlet passage 33 in the head by way of the hollow spigot 14.

In use liquid, for example fuel to be filtered, is delivered through the filter head 8 to the spaces between the sealed ends of the pleats 5 at that end of the element 6. At the other end of the element 6 the spaces between the pleats are
closed, the two halves of the pleats to each side of said spaces being sealed to each other, and the liquid is therefore compelled to pass through the material of the pleats to each side of said spaces and then to pass between the spaces of the pleats at
the inner periphery of the element 6 at said other end and from thence to the openings 22 in the annular base 18 of the filter casing 17 into the bowl 9 where water droplets which have been formed as the liquid fuel passes through the filter paper settle
out at the base of the bowl, the filtered liquid passing upwardly through the center tube 10 and thence to the outlet opening 33 in the filter head 8. This flow path is indicated by the arrows on the left hand portion of FIG. 5.

With the arrangement described the direction of flow of the liquid can be reversed, the liquid to be filtered then being delivered through the center tube 10 and then passing through the openings 22 in the base of the casing 17 of the filter unit
7, then through the spaces between the pleats at the lower end of the element 6, through the walls of the pleats and then through the spaces between the pleats at the upper end of the element, through the openings 31 in the end plate 11 and then out
through the passage 32 to filter head 8.

The construction described above has the desirable advantages that the filter can be used with liquid flow in either direction through the element and that the filter can be readily bled to get rid of air therein before operation.

The casing, center tube and end plate may be formed in sheet metal.

If the center tube has to extend the full length of the filter and the width of the element is not such as to occupy the space between the center tube and casing the modified form of construction of the filter unit 7 shown in FIGS. 6 and 7 may be
employed. In this form of the filter unit, (which is shown with its end plate and center tube made of sheet metal but which could also be made with an end plate and center tube of plastics) the unit 7 is provided with two center tubes one 10 of which,
similarly to the center tube shown in FIG. 5, is engaged by and supports the inner periphery of the element 6, and the other, 51 of which is secured at its ends to the inner periphery of the annular end plate 11 and the inner periphery of the base 18 of
the casing 17. The end plate 11 preferably has interconnected radial and annular channels 52, 53 embossed therein which provide communication between the holes 31 in the end plate 11 and the space between the two center tubes 10, 51 so that air therein
can be vented by way of the channels 52, 53 and holes 31 when the filter 6 is bled to expel air therefrom.